The present invention relates generally to a drive assembly for transmitting power to an automotive power transmission from two power sources. In particular, it pertains to an assembly for driveably connecting an internal combustion (IC) engine and an electric machine to a transmission input.
Hybrid vehicles generally have two power sources, a conventional internal combustion engine, and an alternate power source, such as an electric machine. The electric machine is used as a power source in city driving where vehicle kinetic energy can be recovered by regenerative braking, converted to electric and chemical form, and stored in a battery, from which the motor is driven. The internal combustion is most suitable in highway driving, during which wheel braking and opportunities for energy recovery are infrequent, and the engine operates at its greatest efficiency.
In mixed driving conditions, the electric machine and IC engine may be used together to transmit power to a transmission input shaft, depending on the driving conditions and the magnitude of reserve battery capacity. A compact assembly for alternately combining the output of each power source or connecting them individually to the transmission input, while making efficient use of the radial and axial dimensions of the assembly, is a long sought need in the industry.
The electric machine may be an integrated starter generator (ISG), also known as a combined starter generator, combined starter alternator, or a motor-generator. In a hybrid electric vehicle the ISG assembly may be mounted in line with the engine crankshaft and the vehicle's transmission. In order to provide for proper electromagnetic and dynamic characteristics, energy recovery, thermal properties, packaging dimensions, assembly, and servicing, the ISG powertrain must be carefully designed so that no component impairs the function of another component or of the vehicle.